The NIH Blueprint for Neuroscience Research is a framework for cooperative funding efforts by the NIH Office of the Director and 15 NIH Institutes and Centers that support research on the central and peripheral nervous systems. The Blueprint intends to publish a Request for Applications (RFA) soliciting applications that focus on Tools and Techniques for Elucidating and Manipulating Neural Circuit Development. This RFA, which will utilize the Exploratory/Developmental Research Grant (R21) mechanism, is expected to be published in July 2007. Responsive applications will be directed toward the discovery of novel and/or improved means for precise spatiotemporal analysis or manipulation of circuit assembly in the developing central and peripheral nervous systems. For the purposes of this RFA, neural circuit development is defined as processes occurring during prenatal and postnatal development (through adolescence) that begin with axon and dendrite formation and continue through axon guidance and pathfinding, myelination, synapse formation and synapse refinement. Research funded through this initiative is expected to yield improved tools and technologies to understand normal and aberrant trajectories of circuit development in model systems and/or humans.